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Terrestrial mud volcanoes represent surface features of channels for subsurface methane transport and, therefore, constitute an important source of methane emission from natural environments. How microbial processes regulate methane emissions in terrestrial mud volcanoes has yet to be fully addressed. This study demonstrated the geochemical characteristics and microbial communities of four mud volcano and seep sites in two geological settings of Sicily, Italy. At sites within the accretionary wedge that exhibited higher methane and sulfate concentrations, the communities were dominated by members capable of catalyzing methane and sulfate metabolisms and organic degradation. In particular, both anaerobic and aerobic methanotrophs were abundant and their abundance distribution coincided with the geochemical transition. In contrast, the sites near Mount Etna were characterized by high fluid salinity, CO2, and low methane and sulfate concentrations, with communities consisting of halophilic organic degraders and sulfur metabolizers, along with a minor presence of aerobic methanotrophs. Substantial variations in community composition and geochemistry across spatial and vertical redox gradients suggest that physicochemical contexts imposed by the geology, fluid path, and source characteristics play a vital role in shaping community composition and cycling of methane, sulfur and organic carbon in Sicily mud volcanoes. [ABSTRACT FROM AUTHOR]

The article in the journal "Frontiers in Earth Science" explores contemporary studies on cold seeps, hydrothermal vents, mud volcanoes, and related seafloor features. These features provide insights into deep processes that are typically inaccessible to scientists. The research emphasizes multidisciplinary approaches to studying seafloor fluid emissions, highlighting the importance of geologic, physical, chemical, and biological processes in these environments. The studies cover a wide range of topics, including microbial processes, fluid dynamics, mineralization, and the role of seafloor emissions in global biogeochemical cycles. [Extracted from the article]

The diatom alga Nitzschia cf. thermaloides can be found in large numbers in puddles and lakes in the places where mud volcanoes function in the area of the Bulganak mud volcano field (eastern Crimea). Environmental conditions in such reservoirs are extreme: salinity is from 18 to ≥70‰, insolation is extremely high, and ultraviolet radiation is very strong. The growth rate and the intensity of sexual reproduction of N. cf. thermaloides at different salinity and illumination levels have been studied in laboratory conditions. We have determined the limits of halotolerance and the optima of salinity and illumination for growth and sexual reproduction of the alga, capable of vegetative reproduction in an environment with salinity from 0 to 220‰. The range for sexual reproduction is narrower, from 6 to 54‰. The salinity of 22–25‰ and illumination of about 1.5 klx are optimal for both vegetative and sexual reproduction of N. cf. thermaloides. [ABSTRACT FROM AUTHOR]

Since their creation, geoparks have been among the fastest growing natural environments. Their attractiveness is one of the most important factors for the success of this natural destination. Despite their importance, a bibliometric analysis on geopark attractiveness is missing from the studied databases. The aim of this paper is to synthesise a heterogeneous body of knowledge of geoparks in terms of attractiveness, highlighting the evolution and breadth of the research field. To achieve this, the following objectives were set: (a) to adopt a method based on functions provided by the bibliometrix package to automatically combine databases, namely WoS, Scopus, PubMed and Dimensions, detailing the method used and (b) to analyse the bibliometric indicators in order to identify the trends in the literature and the possible directions for future research. The applied methodology was based on bibliometric analysis using R for non-coders. From the 707 documents retrieved, the validation process resulted in 349 eligible documents published between 2002 and 2024, on which the analysis was carried out. The current study elaborated a method and examined the key information on the topic trends, which were given by production performance, productivity trends, spatial analysis and abstract approach analysis. Additionally, strategic mapping of the conceptual context was performed. Thus, the result provides a description of the automatic method with practical applications. As discerned from the three-dimensional analysis (spatial, temporal and size), the emerging research directions within scientific creativity encompassed (1) forms of tourism practiced in geoparks, especially focused on ecotourism and volcanic tourism; (2) geomorphological features, mineral springs and mud volcanoes; (3) aesthetic aspects, scenic sites and mining heritage; and (4) methodology, data analysis and modelling methods across different regions and countries. [ABSTRACT FROM AUTHOR]

Active and relic marine methane‐seep sites are widely distributed globally and are distinguished by distinctive geology, biogeochemistry, and ecosystems. The discovery of methane‐seep sites in the Krishna‐Godavari (K‐G) basin has created exciting new opportunities for methane‐seep research in the Bay of Bengal. In this study, we document the occurrence of authigenic carbonates, including micro‐crystalline aragonite crust (arg‐crusts) admixed with chemosynthetic shells and high‐magnesium carbonate tubular structures (HMC‐tube), from the methane‐seep site SSD‐045/4 in the K‐G basin. The δ13C values of HMC‐tubes (−54.5 to −46.2‰) and arg‐crusts (−57.6 to −34.8‰) indicate biogenic methane as the likely carbon source. Enhanced porewater alkalinity driving carbonate precipitation may be attributed to microbial‐mediated SO₄2−‐AOM processes. Additionally, δ13C values (−35.2 ± 8‰) of the residual organic matter within the carbonates suggest a contribution of methanotrophic bacterial biomass. The δ18Ocarb values of HMC and aragonite indicate methane hydrate degassing and crystallization pathways, respectively. Pelloid‐filled burrows suggest the reworking of shallow HMC deposit by burrowing organisms, whereas the polyphase cementations (aragonite and HMC) within burrows indicate early and burial diagenetic pathways. The wide range in ΣLREE/ΣHREE ratios and Ceanom values in arg‐crusts reflect micro‐spatial variations in redox conditions, likely due to cementation occurring in both open and closed diagenetic systems. In contrast, more constrained Ceanom values and ΣLREE/ΣHREE ratios in HMC tubes suggest persistent sulfidic conditions. Overall, these findings provide insights into the pathways of carbonate formation at the K‐G basin methane‐seep site, highlighting the complex interplay of microbial processes, fluid dynamics, and diagenetic alterations. Plain Language Summary: Methane cold‐seeps are regions on the seabed where methane (CH4) gas oozes out across the sediment‐water interface into the water column. Both active and inactive seepage sites are known across the oceans. Active methane seep sites expel significant quantities of methane into the seawater which influences the oceanic methane budget as well as the carbon cycle. In contrast, the preserved authigenic carbonate deposits and chemosynthetic fauna at the relic seep sites are archives of past seepage activities. The seep ecosystem comprises a variety of chemosynthetic and non‐chemosynthetic organisms, whereas the geological features include mounds, mud volcanoes, carbonate crusts, chimneys, etc. formed due to methane expulsion processes. Here, we investigate the origin of calcium carbonate structures formed in a cold seep region off the east coast of India. The carbonate structures include tubular‐shaped high magnesian carbonates (HMC) and crusts composed of aragonite minerals. These tubes and crusts archive biological and geological processes, including past variations in methane effusion and diffusion through the sediment. Tubular structures are formed by gas flow through the sediments as chimneys and by burrowing activities of benthic organisms. On the other hand, the aragonite crusts are formed where methane flow is high across the seabed. Key Points: Relics of methanogenic high magnesian calcite tubes and aragonite crust recovered from cold seep site K‐G basin east coast of IndiaHMC precipitation is confined to sulfidic conditions in contrast to a wider redox range for aragonite precipitationReworking of unconsolidated HMC produced the pelloid rich tubular structures, whereas aragonite crust formed at high CH4 flow conditions [ABSTRACT FROM AUTHOR]

Introduction: The Aotearoa New Zealand ghost shrimp of the infraorders Axiidea and Gebiidea have never been comprehensively reviewed, with recent work uncovering a diverse regional fauna representing eight of the 14 known families. Methods: Using standard morphological and DNA sequencing tools, the family Callianopsidae is, for the first time, recorded off New Zealand, represented by a new species of Vulcanocalliax. Results: The new species was found near hydrocarbon seeps on the Hikurangi Margin, on the eastern New Zealand continental slope, and is only the second species now known in this genus. The single congener, V. arutyunovi, is only known from a mud volcano in the Gulf of Cádiz, off the Iberian Peninsula. Vulcanocalliax sp. nov. was formerly reported as an unnamed host of a new endemic New Zealand rhizocephalan barnacle Parthenopea australis and is here formally described as Vulcanocalliax beervana sp. nov. Discussion: The new species differs, e.g., in the shape of the anterior carapace margin (convexly rounded and without elevated postantennal shoulder present in V. arutyunovi), the ocular peduncle having a convex anterolateral margin (compared to a straight margin), and the uropodal exopod has a dorsomedian ridge, lacking the elevated anterior portion that is distinct in V. arutyunovi. This brings the number of described New Zealand ghost shrimp species to 18. A key to all known Callianopsidae is provided. [ABSTRACT FROM AUTHOR]

Areas of the seafloor enriched with seeping fluids host unique chemosynthetic communities, and their interactions not only linked to the presence of oil and gas resources, but directly impact global geochemical cycles. These ecosystems can be found in diverse geological settings, spanning from passive to active continental margins, and encompass environments such as mid-ocean ridges, seamounts, cold brine lakes, mud volcanoes, and carbonate pinnacles. This review aims to examine seep environments in the Western Atlantic, the Caribbean, and Colombia, with a focus on understanding: I) their nature and origin, Itheir associated seabed characteristics, III) the biological communities directly connected to them, and IV) the chemistry and flow of the emitted fluids. The review identifies the close relationship of cold seeps to various geomorphological features, including linear diapir systems, salt diapirs resulting from salt tectonics, regions of mud volcanism, and compact seafloor mounds likely associated with buried mud diapirs. However, existing data on the fauna within these environments predominantly focus on megafauna, such as vestimentiferan tubeworms (Annelida), mussels, and vesicomyid bivalves (Mollusca), overlooking the crucial role of communities of small organisms, including fungi or macrofauna. This review highlights the absence of a consistent consensus among researchers regarding the factors controlling fauna distribution and presence in seep environments. Various authors have put forth divergent factors that influence seep community structures, with some emphasizing water depth, others the geological environment, and some the relationship with geomorphological conditions and fluid emissions. These findings underscore the need for further research into environmental factors and their roles in the observed distribution, presenting a promising avenue for future investigations. [ABSTRACT FROM AUTHOR]

Deep‐sea chemosynthetic ecosystems are 'oases' of life powered by reducing geofluids, of which serpentinite‐hosted seeps are among the least studied. South Chamorro Seamount, a serpentine mud volcano on the Mariana Arc, has been known to host chemosynthesis‐based assemblages since 1996, but no detailed information on the fauna was published. Here, we revisited South Chamorro to characterise its biodiversity. We located two regions of chemosynthetic communities dominated by bathymodioline mussels, vesicomyid clams, and chaetopterid parchment worms: one on the northwestern flank ('Fryer Site') and one on the southern summit ('Summit Site'). We sampled a total of 20 species including 13 molluscs, five annelids, and two crustaceans – all present on the more active Summit Site but only a subset being found at Fryer Site. A mussel bed surrounding the Fryer Site was drilled by the Ocean Drilling Program in 2001 resulting in six holes, the deepest being 266 m (Hole 1200C). Cuttings ~50 cm deep still cover an approximately 60 m radius around Hole 1200C even 22 years later, and there is no sign of recovery. Low geofluid supply in serpentinite‐hosted seamounts may not allow decadal recovery of animal colonies, unlike a previous drilling site in an Okinawa Trough vent. [ABSTRACT FROM AUTHOR]

Diversity of extremophilic microorganisms in mud volcanoes is largely unexplored. Here we report the isolation of a novel alkaliphilic, mesophilic, fermentative bacterium (strain FN5sucT) from a terrestrial mud volcano located at the Taman Peninsula, Russia. Cells of strain FN5sucT are gram-stain-positive, non-sporeforming, motile rods. The temperature range for growth is 10–37°C, with an optimum at 30°C. The pH range for growth is 7.5–10.0, with an optimum at pH 9.0. The isolate utilizes various organic polymeric substances, organic acids, carbohydrates, and proteinaceous compounds. The end products of carbohydrates fermentation are acetate, CO2 and trace amounts of H2 and formate. The major cellular fatty acid compounds are C16:0, C16:1 ω7c, and monounsaturated dimethyl acetal C14:1. Phylogenetic analysis reveals that strain FN5sucT is most closely related to Petrocella atlantisensis = DSM 105309T (98.4% 16S rRNA gene identity). The total size of the genome of strain FN5sucT is 3.35 Mb, and a genomic DNA G+C content is 37.0 mol %. The genome contains complete glycolisis/glyconeogenesis pathway. We propose to assign strain FN5sucT to the genus Petrocella, as a new species, Petrocella pelovolcani sp. nov. The type strain is FN5sucT (=DSM 113898T = UQM 41591T). [ABSTRACT FROM AUTHOR]

Geothermal features, such as hot springs and mud volcanoes, host diverse microbial life, including many extremophile organisms. The physicochemical parameters of the geothermal feature, such as temperature, pH, and heavy metal concentration, can influence the alpha and beta diversity of microbial life in these environments, as can spatiotemporal differences between sites and sampling. In this study, water and sediment samples were collected and analyzed from eight geothermal sites at Yellowstone National Park, including six hot springs, a mud volcano, and an acidic lake within the same week in July 2019, and these geothermal sites varied greatly in their temperature, pH, and chemical composition. All samples were processed and analyzed with the same methodology and taxonomic profiles and alpha and beta diversity metrics determined with 16S rRNA sequencing. These microbial diversity results were then analyzed with respect to pH, temperature, and chemical composition of the geothermal features. Results indicated that predominant microbial species varied greatly depending on the physicochemical composition of the geothermal site, with decreases in pH and increases in dissolved heavy metals in the water corresponding to decreases in alpha diversity, especially in the sediment samples. Similarly, sites with acidic pH values had more similar microbial populations (beta diversity) to one another than to relatively neutral or alkaline pH geothermal sites. This study suggests that pH and/or heavy metal concentration is a more important driver for microbial diversity and population profile than the temperature for these sites and is also the first reported microbial diversity study for multiple geothermal sites in Yellowstone National Park, including the relatively new mud volcano Black Dragon’s Caldron, which erupted in 1948. [ABSTRACT FROM AUTHOR]

This document is a research article published in the journal Frontiers in Microbiology. It acknowledges the contributions of a researcher named Barny to the field of methanogen research and the broader microbial field. The article highlights Barny's work in clarifying the taxonomy of methanogens and recognizes his wider contributions as an editor. The article also includes information about the funding sources for the research and acknowledges the authors and reviewers who contributed to the research topic. It concludes with a statement about potential conflicts of interest and a note from the publisher. [Extracted from the article]

The present work would like to illustrate a new concept of multiparametric stations to characterize the crustal fluids-tectonic interaction in specific geological contexts. The dynamics of crustal fluids in relation to tectonics is a complex and sometimes intricate issue. Several factors act and mutually influence themselves, so that in each tectonic and geological context they follow a specific behavior, and a comprehensive cause-effect rule is hard to find. Changes in water chemistry and levels and in soil flux regimes (e.g., CO2, CH4, radon) are just a few examples well documented in the literature as being pre-, co- and post-seismic modifications as well as being markers of the local tectonic stress acting in the crust. A regional study combined with a long-lasting multiparametric monitoring is needed to prepare to a seismic sequence in a given place. The field infrastructure was set up starting from the end of 2021, and multiparametric stations have been installed in correspondence of active seismogenic sources initially located in Northern Italy. Data are transmitted in real-time and archived in an ad hoc developed relational database. Monitoring is mainly focused on groundwater parameters (water level, temperature, and electrical conductivity) of aquifers showing distinct degrees of confinement and lithologies. Sites are also equipped of meteorological sensors (pressure, temperature, rain, humidity, wind speed and direction), radon sensors and surface and borehole seismic stations providing accelerometric and velocimetric data. A mud volcano field is also monitored and holds the installation of a permanent CO2 soil flux station. A statistical analysis working flow is also proposed for a preliminary evaluation of the acquired time-series. In particular, a couple of tools to detect, and thus filter, anthropogenic and meteorological effects on a groundwater level series is described. We wish to provide a model of approach to analogous study cases in other potentially seismic areas. [ABSTRACT FROM AUTHOR]

Microbial communities of terrestrial mud volcanoes are involved in aerobic and anaerobic methane oxidation, but the biological mechanisms of these processes are still understudied. We have investigated the taxonomic composition, rates of methane oxidation, and metabolic potential of microbial communities in five mud volcanoes of the Taman Peninsula, Russia. Methane oxidation rates measured by the radiotracer technique varied from 2.0 to 460 nmol CH4 cm−3 day−1 in different mud samples. This is the first measurement of high activity of microbial methane oxidation in terrestrial mud volcanos. 16S rRNA gene amplicon sequencing has shown that Bacteria accounted for 65–99% of prokaryotic diversity in all samples. The most abundant phyla were Pseudomonadota, Desulfobacterota, and Halobacterota. A total of 32 prokaryotic genera, which include methanotrophs, sulfur or iron reducers, and facultative anaerobes with broad metabolic capabilities, were detected in relative abundance >5%. The most highly represented genus of aerobic methanotrophs was Methyloprofundus reaching 36%. The most numerous group of anaerobic methanotrophs was ANME-2a-b (Ca. Methanocomedenaceae), identified in 60% of the samples and attaining relative abundance of 54%. The analysis of the metagenome-assembled genomes of a community with high methane oxidation rate indicates the importance of CO2 fixation, Fe(III) and nitrate reduction, and sulfide oxidation. This study expands current knowledge on the occurrence, distribution, and activity of microorganisms associated with methane cycle in terrestrial mud volcanoes. [ABSTRACT FROM AUTHOR]

Seismic signals generated by mud volcanoes could be used to monitor gas emission. To this end, a seismic array of vertical geophones and three-directional velocimeters have been deployed close to major emission cones in the Nirano mud volcano area, in the northern Apennines. A detailed analysis of the resulting time series has been performed both in time and spectral domains, revealing the existence of three distinct kinds of signals: background noise, paroxysmal phases (drumbeats), and regular sequences of identical pulses (drumrolls). Both drumbeats and drumrolls are characterised by higher frequencies than the background seismic noise. Drumbeats show relatively high amplitudes and long durations (in the order of several seconds) but an irregular time pattern, while drumrolls are constituted by very regular sequences of almost identical short (less than 1 s) monochromatic pulses. Both drumbeats and drumrolls appear to be constituted by S waves, originated locally in the same shallow subsoil area, close to the main vents. These seismic signals could be related to the mechanical interaction of shallow solid conduits with a two-phase (mud and gas) slug flow from depth, which is characterised by irregularly spaced long bubbles (drumbeats), alternated with trains of small bubbles (drumrolls). [ABSTRACT FROM AUTHOR]

The mud volcanoes of Sivan region are unique phenomena that are closely related to the folded and fine- grained sedimentary units of the Miocene. These mud volcanoes are in the form of eroded and inactive or semi-active cones, as well as mud ponds in the region. The results of the analysis of the sediment samples, in terms of texture, place them in the mudstone and clayey silt groups, in the Folk and Shepard classifications, respectively. Quartz, feldspars, mica, various heavy minerals, clay minerals (Illite and chlorite) and rock fragments (metamorphic, carbonate and volcanic) are the components of these sediments. Mineralogical evidence indicates the origin of sediments from metamorphic and possibly volcanic rocks of the region. The amount of calcium carbonate in the mud samples varies between 19 and 45%, and accordingly, the sediments of the mud volcanoes are calcareous mud, argillaceous marl, and marl. The formation of Sivan mud volcanoes can be related to some factors such as the presence of fine-grained sediments of Miocene, the thickness of sediments, and the influence of overburden pressures and regional tectonics. Also, the presence of a hidden salt dome according to the geological map as well as surface features can be effective factor in the formation and activity of the mud volcanoes in this area. In terms of the composition of sediment, water and formation mechanism, these mud volcanoes are comparable to mud volcanoes on the margins of the Caspian basin, which can be related to their sedimentation-tectonic conditions. [ABSTRACT FROM AUTHOR]

A novel aerotolerant anaerobic bacterium (strain M4AhT) was isolated from a terrestrial mud volcano (Taman Peninsula, Russia). Cells were small, cell-wall-less, non-motile cocci, 0.32–0.65 μm in diameter. The isolate was a mesophilic, neutrophilic chemoorganoheterotroph, growing on carbohydrates (D-glucose, D-trehalose, D-ribose, D-mannose, D-xylose, D-maltose, D-lactose, D-cellobiose, D-galactose, D-fructose, and D-sucrose), proteinaceous compounds (yeast extract, tryptone), and pyruvate. Strain M4AhT tolerated 2% oxygen in the gas phase, was catalase-positive, and showed sustainable growth under microaerobic conditions. The dominant cellular fatty acids of strain M4AhT were C16:0 and C18:0. The G+C content of the genomic DNA was 32.42%. The closest phylogenetic relative of strain M4AhT was Mariniplasma anaerobium from the family Acholeplasmataceae (order Acholeplasmatales, class Mollicutes). Based on the polyphasic characterization of the isolate, strain M4AhT is considered to represent a novel species of a new genus, for which the name Peloplasma aerotolerans gen. nov., sp. nov. is proposed. The type strain of Peloplasma aerotolerans is M4AhT (=DSM 112561T = VKM B-3485T = UQM 41475T). This is the first representative of the order Acholeplasmatales, isolated from a mud volcano. [ABSTRACT FROM AUTHOR]

Virtual reality is a technological development that, among others, has revolutionized Earth sciences. Its advantages include an opportunity to examine places otherwise difficult or impossible to access and it may also become an important component of education, fostering a better understanding of processes and landforms, geohazard awareness, and an appreciation of geoheritage. This paper reports on the GeoVT project, which aims to create a platform to build and disseminate Virtual Field Trips (VFTs) focused on geomorphology, natural hazards associated with geomorphological processes, and geoheritage sites. To put the GeoVT project in context, an overview of applications of VR in geosciences is provided. This paper subsequently proceeds with a presentation of the project and the GeoVT Authoring application, which is an innovative platform designed to help teachers and students, followed by brief presentations of a number of VFTs developed within the project. They address themes such as fluvial landforms and valley development, coastal landforms, evidence of past glaciation, coastal erosion, wildfire effects, mud volcanoes, and landslides. [ABSTRACT FROM AUTHOR]

Multiple liquefaction events may occur if a seabed is subjected to repeated but intermittent wave loadings. This study aimed to investigate the influence of the wave-loading history on the evolution of residual liquefaction in a silty seabed through a series of wave flume tests. The flume observations reveal that the preceding wave-loading history results in the densification of the silt bed and a noticeable settlement of the mudline. Meanwhile, the ultimate liquefaction depth, maximum amplitude of interfacial waves, and mudline settlement decrease due to prior wave actions. Both the maximum residual pore pressure ratio and the amplification ratio of transient pore pressure exhibit a declining trend with an increasing number of wave exposures, indicating that the liquefaction resistance of the soil is obviously enhanced. Throughout the continuous liquefaction stage, the residual pore pressure in liquefied soil regions maintains its maximum value. In contrast, the pore pressure in the un-liquefied soil layer experiences slight dissipation after reaching its peak during wave activity. Moreover, the reshaped topography of the silt bed following liquefaction-densification cycles may serve as an indicator of prior liquefaction events, transforming from mud volcanoes into ripples as the liquefaction depth decreases. [ABSTRACT FROM AUTHOR]

One of the most promising applications of satellite data is providing users in charge of land and emergency management with information and data to support decision making for geohazard mapping, monitoring and early warning. In this work, we consider ground displacement data obtained via interferometric processing of satellite radar imagery, and we provide a novel post-processing approach based on a Functional Data Analysis paradigm capable of detecting precursors in displacement time series. The proposed approach appropriately accounts for the spatial and temporal dependencies of the data and does not require prior assumptions on the deformation trend. As an illustrative case, we apply the developed method to the identification of precursors to a mud volcano eruption in the Santa Barbara village in Sicily, southern Italy, showing the advantages of using a Functional Data Analysis framework for anticipating the warning signal. Indeed, the proposed approach is able to detect precursors of the paroxysmal event in the time series of the locations close to the eruption vent and provides a warning signal months before a scalar approach would. The method presented can potentially be applied to a wide range of geological events, thus representing a valuable and far-reaching monitoring tool. [ABSTRACT FROM AUTHOR]

With the rapid development of aeromagnetic (primarily uncrewed) methods for measuring the magnetic field, the possibility of detailed magnetic research in hard-to-reach mountainous areas, forested areas, swamp areas, desert areas, and water areas has emerged. The conditions for interpreting the magnetic field are most difficult due to the vector nature of the magnetic properties of rocks, the wide range of their properties, and the presence of residual magnetization. The physical and geological conditions of the territory of Azerbaijan are characterized by rugged terrain relief, inclined magnetization (~58°), and complex geological environments. Along with using a probabilistic approach, deterministic methods for solving inverse and direct problems of geophysics become of great importance since it is possible to identify relatively extended reference boundaries and analyze magnetic anomalies from separate bodies of relatively simple shape. The article briefly outlines the main stages of processing and interpreting magnetic data under complex environments. The theoretical examples discussed include a block diagram of various disturbances, interpretive models of thin and thick beds, an intermediate model, a thin horizontal plate, and a horizontal circular cylinder on the flat and inclined surfaces under inclined magnetization conditions. The process of assessing magnetization on sloping terrain relief is shown. The presented field examples for the Caucasus Mountains show the quantitative interpretation of aeromagnetic data at the Big Somalit and Guton sites (southern Greater Caucasus, Azerbaijan), a deep regional profile through the Lesser and Greater Caucasus, magnetic field studies in the area around the Saatly superdeep borehole (Middle Kur depression between the Greater and Lesser Caucasus), and 3D magnetic field modeling at the Gyzylbulag gold deposit (the Azerbaijani part of the Lesser Caucasus). In the Caspian Sea, we demonstrated the use of an information parameter to identify faults in the Bulla hydrocarbon field (Gulf of Baku) and, for the first time, obtained the relationship between the generalized aeromagnetic data (2.5 kilometers over the mean sea level) and the central area of the mud volcanoes distribution in Azerbaijan. [ABSTRACT FROM AUTHOR]

Featured Application: Deep geoelectrical mapping of subsurface objectives. This work presents a case study of a geoelectrical exploration of understudied mud volcanoes in Romania, specifically the Pâclele Mici mud volcano from Buzău County. Using a geoelectrical technique facilitated by the distributed network of V-FullWaver equipment, we present, to our knowledge, the first deep 3D case study of a mud volcano in the country. The findings indicate that while geoelectrical surveys in such environments are met with important challenges in terms of soil conductivity, they nonetheless provide a viable approach to uncovering the complex structures and processes of mud volcanoes. We map a part of the mud volcano, showing that the active subsurface part corresponds only partly with what is visible on the surface, and suggest a framework for an in-depth analysis of the extensive mud volcano area. [ABSTRACT FROM AUTHOR]

The paper presents the results of a study of carbonate and sulfate–carbonate–clayey rocks of the Lower Maeotian in the sections of the bays of Cape Kazantip using a complex of analytical methods. It is established that the greatest variation of chemical, bituminological, phase, and carbon-isotope composition is characterized by carbonate–clay and clayey rocks of the section bottom. It is proved that the initial OM was accumulated mainly under reducing conditions, but has some variations in composition; it is characterized by a low degree of its catagenetic transformation, which indicates the preservation of the primary isotopic composition. The diverse phase composition of the clay fraction is revealed: dioctahedral illite, kaolinite, chlorite, glauconite, and weakly ordered mixed-layer formations of illite/smectite type with different ratios of illite and smectite components and varying degrees of ordering. Modeling of their diffraction profiles showed that the illite/smectite structure may indicate significant depths of sediment mobilization by mud volcanoes. The isotopic composition of the 13Сorg ranges widely from –33.72 to –19.27‰ the mode being –22.1...–24.93‰. The isotopic composition of 13Сorg below –25.6‰ may be related to the entry of isotope-light mass of methane-oxidizing bacteria into the OM. It was revealed that variations of isotopic composition curves 13Сcarb and 13Сorg along the section of the studied rocks are rarely characterized by unidirectional (positive or negative) variations and have different trends along the section. Direction of the 13Сcarb isotope composition curve with some variations has a pronounced upward trend toward heavier weighting, whereas the isotopic values of the 13Сorg reveals reverse tendency. The results obtained prove that the revealed variations in the composition of OM and carbon isotope composition in the Lower Maeotian sections of Cape Kazantip reflect variations in the sedimentation conditions of temperature, salinity, freshwater ingression, bioproductivity fluctuations, and the influence of local gas–fluid deposition. It is proposed to use such accessory minerals as zircon, monazite, and ilmenite as an indicator of mud paleovolcanism. [ABSTRACT FROM AUTHOR]

Areas of the seafloor enriched with seeping fluids host unique chemosynthetic communities, and their interactions not only linked to the presence of oil and gas resources, but directly impact global geochemical cycles. These ecosystems can be found in diverse geological settings, spanning from passive to active continental margins, and encompass environments such as mid-ocean ridges, seamounts, cold brine lakes, mud volcanoes, and carbonate pinnacles. This review aims to examine seep environments in the Western Atlantic, the Caribbean, and Colombia, with a focus on understanding: I) their nature and origin, Itheir associated seabed characteristics, III) the biological communities directly connected to them, and IV) the chemistry and flow of the emitted fluids. The review identifies the close relationship of cold seeps to various geomorphological features, including linear diapir systems, salt diapirs resulting from salt tectonics, regions of mud volcanism, and compact seafloor mounds likely associated with buried mud diapirs. However, existing data on the fauna within these environments predominantly focus on megafauna, such as vestimentiferan tubeworms (Annelida), mussels, and vesicomyid bivalves (Mollusca), overlooking the crucial role of communities of small organisms, including fungi or macrofauna. This review highlights the absence of a consistent consensus among researchers regarding the factors controlling fauna distribution and presence in seep environments. Various authors have put forth divergent factors that influence seep community structures, with some emphasizing water depth, others the geological environment, and some the relationship with geomorphological conditions and fluid emissions. These findings underscore the need for further research into environmental factors and their roles in the observed distribution, presenting a promising avenue for future investigations.

Fluid conduits play important roles in the dynamic evolution processes of marine gas hydrate systems (GHS), but detailed analysis of these specific roles has been inadequate. In this paper, various types of gas hydrate-related fluid conduits are analysed by examining abundant global case studies mainly using seismic data, and the interaction of these fluid conduits with the GHS is analysed. Results show that faults and gas chimneys are the most common fluid conduits, accounting for ~80% of the analysed GHS-related conduits. Other fluid conduits include permeable dipping strata, polygonal faults, mud/salt diapirs, mud volcanoes, and unconformity surfaces. Two groups of fluid conduits can be classified according to their roles for the GHS. Group 1 fluid conduits mainly exist underneath the GHS which transported deeper gas upwards to the GHS, providing gas source to form gas hydrates or the underlying free gas zone (FGZ). Group 2 fluid conduits are less in quantity compared to group 1, accounting for ~28% of the analysed conduits and often located at shallower depth within the GHS. When the FGZ is critically pressured due to the continuous accumulation of free gas or gas hydrates dissociate, group 2 fluid conduits may be triggered or reactivated, channelling free gas to the shallower layers or even the seabed. Group 1 fluid conduits mainly play a positive role in the formation of the GHS, while group 2 fluid conduits may play a role in affecting the seabed ecosystem or even climate change due to the gas escape to the seabed or even the sea water. Generally, this classification method can help better understand the roles of fluid conduits for the GHS, which should be widely applicable in other gas hydrate study areas. [ABSTRACT FROM AUTHOR]

The acid–base properties of the surface of Maikop series clays and mud volcano clays, as well as their adsorption properties with respect to mercury(II) ions, were studied. It is shown that pHPZC for the former is 7.1 on average; for the latter, 9.0. The pHPZC value for mud volcano clays is consistent with the pH values in the waters of mud volcanoes of the Kerch–Taman region. When the mass ratio of the sorbent and solution is 1 : 900, adsorption equilibrium occurs after 4 days with active stirring. Experimental data on mercury adsorption from NaCl–NaHCO3 solution on natural sorbents are best described by the Redlich–Peterson and Toth equations. The process of mercury adsorption on clays of the Maikop series is more intense than that on mud volcano clays. [ABSTRACT FROM AUTHOR]

This article presents a comparative analysis of the isotope-geochemical characteristics of the products of activity of mud volcanoes (MVs) in the northwestern (Azerbaijan) and southeastern (Iran) parts of the South Caspian Basin (SCB). Gases of MVs in the studied regions are mainly of thermocatalytic origin, with the predominance of methane. High concentrations of nitrogen (up to 50%) are noted in the gases of some MVs in the Iranian sector. One distinctive feature of the MVs in the Azerbaijani part of the SCB is the presence of isotopically superheavy (>5‰) carbon dioxide, which is not typical for MVs in Iran. The waters of the MVs of Iran and most of the MVs of Azerbaijan are of the sodium chloride type. Isotopically heavy bicarbonate and carbonate ions, characteristic of the mud volcanic waters of Azerbaijan, are not typical for the volcanoes of the Iranian part of the SCB. Organic matter of rock ejecta of MVs in the Azerbaijani part of the SCB refers mainly to type II and type II–III kerogen, while in its Iranian part it is mainly type III kerogen. Mud volcanoes of Azerbaijan are characterized by a wide range of gas generation depths (10–16 km) and, accordingly, significant subvertical migration. The calculated maximum depth of the HC gas source in the Iranian part of the SCB does not exceed 12 km. [ABSTRACT FROM AUTHOR]

We identified 27 new mud volcanoes, including potential ones, in a part of the Hyuga-nada area, southwest offshore Japan, at the northern end of the Ryukyu Trench, based on subseafloor geological structures using geophysical investigations. These mud volcanoes exhibited high density and breadth and were likely connected to other mud volcano fields in the south. Acoustic investigations indicated subseafloor structures. Multiple acoustically transparent bodies were interpreted as a region containing gas. They were likely to appear along faults and below the bottom of valleys and sometimes reached the seafloor, expressing mud volcanoes onto the seafloor. They also indicated the wide distribution of subseafloor free-gas throughout the area. These acoustic investigations suggested that a swarm of mud volcanoes exists over the Hyuga-nada area, heterogeneously distributed along a series of plate convergent margins, the Nankai Trough, and the northern part of the Ryukyu Trench. [ABSTRACT FROM AUTHOR]

Mud volcanoes (MVs) are surface structures typically created by episodic discharge of fluids and solids, often associated to onshore and offshore accretionary prisms on convergent plate boundaries. Detailed investigations of ongoing activity and its associated morphological changes, as well as a better understanding of the temporal evolution of these highly dynamic systems, may improve the estimations of material fluxes from MVs drastically. Until today, approximately 70 individual MVs were discovered in the northern Ionian Sea in the Calabrian Arc (Central Mediterranean Sea), but only a few have been analyzed and described in detail. In this study, new evidence for recent recurring eruptive activity of the ~45 m-high and 1 km-wide Sartori MV situated in the clastic wedge of the Calabrian Arc is presented. High-resolution seafloor mapping as well as sediment temperature, geochemical, and sedimentological data received from two research cruises in 2016 and 2020 are used. Bathymetric and seafloor backscatter data (1 m scale) indicate the presence of two active eruption centers at the flat-topped Sartori MV. Elevated sediment temperature gradients at both eruption centers show that currently heat is transferred to the surface sediments. Pore water analyses indicate that fluids rising below the eruption centers are CH4-rich, Cl--poor, and SO42--free. Stable C and H isotopic compositions of methane suggest that it originates from a mix of primary microbial, secondary microbial, and/or thermogenic sources. A relatively shallow position of the sulfate-methane interface at both eruption centers also indicates the presence of upward fluid migration in recent times. Pore water modeling suggests that seawater has penetrated the surface sediments to a greater extent within the last few years. In contrast, centimeter-thick layers of hemipelagic sediments overlying mud breccia in sediment cores taken from both eruption centers show that no solid material has been ejected in recent times. Sediment core analyses combined with high-resolution seafloor mapping show an absence of rim-passing mudflows over the past ~10 ka. It is concluded that Sartori MV is an episodically active MV from which fluids with a comparatively low flux were released into the bottom water in recent times. [ABSTRACT FROM AUTHOR]

Buried mounds have been identified on seismic reflection profiles in the southern Roosevelt sub-basin of the eastern Ross Sea, Antarctica. Since they have never been sampled, the composition of these mounds can only be inferred from their acoustic character. Previous studies have hypothesised that they are buried glacial moraines deposited by ice grounding near the paleo-continental shelf edge, suggesting the beginning of the growth of the West Antarctic Ice Sheet (WAIS) as early as the late Oligocene. This hypothesis conflicts with earlier evidence of the WAIS advance over the central-eastern Ross Sea. An alternative explanation for the origin of the mounds, as mud volcanoes, is formulated here on the basis of seismic reflection profile reprocessing and comparison with other, better studied, mound provinces in the Ross Sea. Shallow drilling is required to verify, which hypothesis is correct, and this has implications for various WAIS scenarios, ice volumes, and thermal rheological modelling. [ABSTRACT FROM AUTHOR]

Outcrops of the coal-bearing Tankhoi Formation (Oligocene–Pliocene), traced along the southern shore of Lake Baikal, submerge under its Southern Basin, where several hydrate-bearing zones of the focused hydrocarbon fluid discharge have been found. To test the hypothesis that coals of the Tankhoi Formation can be the sources of hydrocarbon gases in these zones, we collected coal samples from the Shakhterskaya Gorka outcrop. Experiment on gas generation from the selected samples was carried out in a special autoclave at a temperature of 90°C for eight months. This paper presents the obtained results, which confirm an important role of the process of gas generation from coals in the formation of fluids in the Kedr mud volcano. The further migration of gases was accompanied by the biodegradation and formation of secondary microbial methane due to CO2 reduction. This was one of the reasons for the carbon isotopic pattern observed in methane (heavier than –50‰ VPDB) and carbon dioxide (positive values) taken from the near-surface sediments and hydrates of the Kedr mud volcano, as well as for the significant enrichment of authigenic siderites in the heavy 13C isotope. [ABSTRACT FROM AUTHOR]

Mud volcanoes are geological structures observed throughout the world that arise from the upwelling of deep fluids along discontinuities in the subsoil. The detection of mud fluid migration pathways can be challenging, even when using Electrical Resistivity Tomography (ERT) as detectability issues may arise from complex geological settings. This paper presents new results from 2D and 3D ERT synthetic modelling for the investigation of the shallow, internal structure of terrestrial mud volcanoes. This study revealed the internal structure of the 'Cenerone-Pineto' mud volcano (Central Italy) and provided further clues as to its internal structure. The main results of the study are: the presence of a mud chamber, which represents the last phase of mud accumulation before final emission, not located beneath the crater but laterally offset, as well as the presence of a narrow, shallow feeder channel; these findings represent evidence of a much more complex structure than one would expect. This means that the mud volcano is not supplied with mud fluids directly from below as would be the case with an uprising of deep fluid along a near-vertical open fracture and that the shallow mud fluid reservoir is not correlated to the distribution of any mud volcano observed on the surface. Findings from this study are consistent with the observed structural features already noted in ERT and seismic field data collected at the 'Cenerone-Pineto' mud volcano and may be helpful in explaining the mechanisms and processes involved in mud volcanism in similar geological settings. [ABSTRACT FROM AUTHOR]

Subtle mounds have been discovered in the source areas of Martian kilometer‐sized flows and on top of summit areas of domes. These features have been suggested to be related to subsurface sediment mobilization, opening questions regarding their formation mechanisms. Previous studies hypothesized that they mark the position of feeder vents through which mud was brought to the surface. Two theories have been proposed: (a) ascent of more viscous mud during the late stage of eruption and (b) expansion of mud within the conduit due to the instability of water under Martian conditions. Here, we present experiments performed inside a low‐pressure chamber designed to investigate whether the volume of mud changes when exposed to a Martian atmospheric pressure. Depending on the mud viscosity, we observe a volumetric increase of up to 30% at the Martian average pressure of ∼6 mbar. The reason is that the low pressure causes instability of the water within the mud, leading to the bubble formation that increases the volume of the mixture. This mechanism bears resemblance to the volumetric changes associated with the degassing of terrestrial lava or mud volcano eruptions caused by a rapid pressure drop. We conclude that the mounds associated with putative Martian sedimentary volcanoes might indeed be explained by volumetric changes in the mud. We also show that mud flows on Mars and elsewhere in the Solar System could behave differently to those found on Earth because mud dynamics are affected by the formation of bubbles in response to the different atmospheric pressures. Plain Language Summary: Mars is a planet whose surface atmospheric pressure is ∼160 times weaker than that on Earth. This means that water cannot be present on the Mars surface since in these conditions, lit should boil and evaporate. At the same time, many edifices previously observed on the planet's surface are believed to be the result of mud movement over the Martian surface. Many authors proposed that these structures are the result of a process of sedimentary volcanism during which the sediment was mobilized by liquid water. However, until now, it remained unclear how muds of various viscosities would behave under current Martian conditions. Here, we show that depending on the mud viscosity, a volumetric increase in up to 30% might occur. The reason is that the low pressure causes instability of the water within the mud, leading to the formation of bubbles that increase the volume of the mud mixture. This shows that mud flows on Mars and elsewhere in the Solar System could behave differently to those found on Earth and therefore we might encounter different shapes of edifices formed on Mars by sedimentary volcanism than on Earth. Key Points: High viscosity muds are able to prevent the easy escape of water vapor bubbles leading to the increase in the volume of such mixturesDepending on the thickness of the mudflow, the volumetric increase can reach up to 30% and thus change the resulting shape of the mudflowPresence of small mounds associated with putative Martian sedimentary volcanoes might be explained by volumetric changes in the mud [ABSTRACT FROM AUTHOR]

This work presents original data on the contents and distribution of major and rare earth elements in the waters from 26 mud volcanoes within the Kerch–Taman region. In terms of the chemical composition, the studied mud volcanic waters are the Na–Cl and Na–HCO3–Cl types. However, the Cl/Br, Na/Cl, and Y/ Ho ratios indicate three main genetic groups of volcanoes. It was found that the contents of the rare earth elements in the aqueous phase of mud volcanoes are low (fractions of μg/L) and are distinguished by negative cerium anomalies and positive europium and holmium anomalies. The highest REE concentrations are observed in the mud volcanoes located within the oldest Cretaceous sediments in the area of fault influence. As the distance from the Mesozoic source ΣREE dramatically decreases, it was revealed that the free CO2 content in the aqueous phase regulates the REE content in waters and the cerium and europium anomalies. [ABSTRACT FROM AUTHOR]

The Guaymas Basin in the Gulf of California is characterized by active seafloor spreading, the rapid deposition of organic-rich sediments, steep geothermal gradients, and abundant methane of mixed thermogenic and microbial origin. Subsurface sediment samples from eight drilling sites with distinct geochemical and thermal profiles were selected for DNA extraction and PCR amplification to explore the diversity of methane-cycling archaea in the Guaymas Basin subsurface. We performed PCR amplifications with general (mcrIRD), and ANME-1 specific primers that target the alpha (α) subunit of methyl coenzyme M reductase (mcrA). Diverse ANME-1 lineages associated with anaerobic methane oxidation were detected in seven out of the eight drilling sites, preferentially around the methane-sulfate interface, and in several cases, showed preferences for specific sampling sites. Phylogenetically, most ANME-1 sequences from the Guaymas Basin subsurface were related to marine mud volcanoes, seep sites, and the shallow marine subsurface. The most frequently recovered methanogenic phylotypes were closely affiliated with the hyperthermophilic Methanocaldococcaceae, and found at the hydrothermally influenced Ringvent site. The coolest drilling site, in the northern axial trough of Guaymas Basin, yielded the greatest diversity in methanogen lineages. Our survey indicates the potential for extensive microbial methane cycling within subsurface sediments of Guaymas Basin. [ABSTRACT FROM AUTHOR]

The quest for past Martian life hinges on locating surface formations linked to ancient habitability. While Mars' surface is considered to have become cryogenic ~3.7 Ga, stable subsurface aquifers persisted long after this transition. Their extensive collapse triggered megafloods ~3.4 Ga, and the resulting outflow channel excavation generated voluminous sediment eroded from the highlands. These materials are considered to have extensively covered the northern lowlands. Here, we show evidence that a lacustrine sedimentary residue within Hydraotes Chaos formed due to regional aquifer upwelling and ponding into an interior basin. Unlike the northern lowland counterparts, its sedimentary makeup likely consists of aquifer-expelled materials, offering a potential window into the nature of Mars' subsurface habitability. Furthermore, the lake's residue's estimated age is ~1.1 Ga (~3.2 Ga post-peak aquifer drainage during the Late Hesperian), enhancing the prospects for organic matter preservation. This deposit's inferred fine-grained composition, coupled with the presence of coexisting mud volcanoes and diapirs, suggest that its source aquifer existed within abundant subsurface mudstones, water ice, and evaporites, forming part of the region's extremely ancient (~ 4 Ga) highland stratigraphy. Our numerical models suggest that magmatically induced phase segregation within these materials generated enormous water-filled chambers. The meltwater, originating from varying thermally affected mudstone depths, could have potentially harbored diverse biosignatures, which could have become concentrated within the lake's sedimentary residue. Thus, we propose that Hydraotes Chaos merits priority consideration in future missions aiming to detect Martian biosignatures. [ABSTRACT FROM AUTHOR]

The gas hydrate‐bearing structure—mud volcano Kedr‐1 (Lake Baikal, southern basin)—is located near the coal‐bearing sediments of the Tankhoy formation of Oligocene–Miocene age and can be an ideal source of gas‐saturated fluid. A significant amount of siderite minerals (FeCO3) were collected from sediments at depths ranging from 0.5 to 327 cm below the lake floor (cmblf). An important feature of these carbonate minerals is the extremely strong enrichment in the heavy 13C isotope, reaching values of +33.3‰ VPDB. The δ13C of the siderite minerals, as well as their morphology and elemental composition, and the δ13CDIC of the co‐existing pore water, differed across layers of the core, which implies at least two generations of siderite formation. Here, we leverage mineralogical and geochemical data with 16S rRNA data from the microbial communities in sediments surrounding layers containing siderite minerals. Statistical data reveal the formation of three clusters of microbial communities based on taxonomical composition, key taxa among bacteria and archaea, and environmental parameters. Diversity and richness estimators decrease with sediment depth, with several similar prevailing clades located at the bottom of the core. Most of the taxa in the deep sediments could be associated with putative metabolisms involving organotrophic fermentation (Bathyarchaeia, Caldatribacteriota, and Chloroflexota). Various groups of methanogens (Methanoregulaceae, Methanosaetaceae, and Methanomassiliicoccales) and methanotrophic (Methanoperedenaceae) archaea are present in the sediment at variable relative abundances throughout the sampled depth. Based on the physicochemical characteristics of the sediment, carbon isotope analysis of carbonate minerals and DIC, and phylogenetic analysis of individual taxa and their metabolic potential, we present several models for subsurface siderite precipitation in Lake Baikal sediments. [ABSTRACT FROM AUTHOR]

Slab dehydration at subduction zones has broad implications for arc magmatism, mantle heterogeneity and elemental cycling. We present the petrography, mineral chemistry and whole-rock potassium (K) and lithium (Li) isotopic compositions of subducted metabasites exhumed from serpentinite mud volcanoes from the Mariana forearc that were recovered during International Ocean Discovery Program Expedition 366, to evaluate the capability of K and Li isotopes for tracking slab dehydration and the evolution of the slab-derived fluids at shallow subduction zones. The results show that the δ41K values of HIMU-type alkali metabasites recovered from the shallow-sourced site (i.e., Fantangisña, −0.34 ± 0.06‰, 2SD, n = 3) are slightly higher than those from the deep-sourced site (i.e., Asùt Tesoru, −0.42 ± 0.20‰, 2SD, n = 8). In addition, all the HIMU-type metabasites have homogeneous radiogenic isotope compositions (e.g., Sr, Nd and Hf), and the clinopyroxenes therein show similar trace elements patterns, indicating they have a common mantle source. These observations together with the positive correlation between δ41K and δ11B suggest that K isotope fractionation most likely resulted from metamorphic dehydration. In contrast, no such correlation was observed for Li isotopes (δ7Li ranging from +3.7‰ to +6.6‰). The Li isotope compositions can be modeled by low-temperature fluid/rock interactions with varying water/rock ratios, implying that the Li isotopic system was mainly controlled by fluid metasomatism within the subduction channel. Notably, EM-II-type metabasites have the lightest K isotope compositions (−0.72‰ to −0.67‰) and heaviest Li isotope compositions (+8.1‰ to +8.3‰) in this study. These anomalous signatures were accompanied with the lowest Nb/Th, ε Nd (t) and ε Hf (t), indicating that the K and Li isotope data of EM-II-type metabasites were indicative of their mantle source (e.g., EM-II mantle reservoir). Rayleigh fractionation modeling illustrates that the deeply subducted metabasites are characterized by high K and Li concentrations, and low δ41K, but MORB-like δ7Li. Thus, they may transfer large amounts of fluid-mobile elements into the deep mantle that contributes to the K isotopic heterogeneity in the mantle. [ABSTRACT FROM AUTHOR]

The debate about the conceptual model of mud volcanoes functioning is still alive in the literature. A large part of the literature focuses on the characterization of the deep reservoir where expelled fluids are expected to originate. Another part of literature is focused on the study of the shallow system of mud volcanoes, which could influence the short‐term variations in mud volcanoes activity. We present and analyze a new data set of micro‐gravimetric data to study the area of the Nirano Salse, Italy. Unlike what is commonly assumed for the study area, our results suggest that the geomorphology of the Nirano Salse is not related to a caldera collapse above a shallow mud chamber, but to the surface expression of slip distribution of a fault termination along which the fluids ascended to the surface. We believe that gravimetric data can significantly improve the study of hydrocarbon seeps and mud volcanism. Plain Language Summary: Mud volcanoes are broadly distributed throughout the globe, both on‐and off‐shore. They are formed by the episodic eruption of mud and rock fragments. The eruptions are mainly driven by of gravitative instability, due to the overall low density of clay on surrounding soil types and fluid overpressures. To date, a physical conceptual model of the area of Nirano Salse (Northern Italy), ascribes the mud eruptions to the presence of over‐pressurized fluids that are expelled from a main deep reservoir. The latter is put into communication with the surface due to the episodical reactivation of pre‐existing faults or pipes. The debate about this conceptual model is still open. To improve it, a new data set of gravimetric data was acquired during 2022. Our results suggest that the morphology of the study area is due to the presence of an almost vertical fault, which acts as a preferential route for the ascent of deep fluids. Key Points: A microgravimetric survey coupled with laboratory density measurements allows to image the shallow to medium subsurface below mud volcanoesGravimetric data allow to distinguish between morphologies due to caldera collapse and the surface expression of slip along a faultFor the first time the attenuation volume caused by mud intrusion is imaged by gravimetry along a fault [ABSTRACT FROM AUTHOR]

Highly purified cultures of alkaliphilic aceticlastic methanogens were collected for the first time using methanogenic enrichments with acetate from a soda lake and a terrestrial mud volcano. The cells of two strains were non-motile rods forming filaments. The mud volcano strain M04Ac was alkalitolerant, with the pH range for growth from 7.5 to 10.0 (optimum at 9.0), while the soda lake strain Mx was an obligate alkaliphile growing in the pH range 7.7-10.2 (optimum 9.3-9.5) in the presence of optimally 0.2-0.3 M total Na+. Genomes of both strains encoded all enzymes required for aceticlastic methanogenesis and different mechanisms of (halo)alkaline adaptations, including ectoine biosynthesis, which is the first evidence for the formation of this osmoprotectant in archaea. According to 16S rRNA gene phylogeny, the strains possessed 98.3-98.9% sequence identity and belonged to the obligately aceticlastic genus Methanothrix with M. harundinaceae as the most closely related species. However, a more advanced phylogenomic reconstruction based on 122 conserved single-copy archaeal protein-coding marker genes clearly indicated a polyphyletic origin of the species included in the genus Methanothrix. We propose to reclassify Methanothrix harrundinacea (type strain 8AcT into a new genus, Methanocrinis gen. nov., with the type species Methanocrinis harrundinaceus comb. nov. We also propose under SeqCode the complete genome sequences of strain MxTs (GCA_029167045.1) and strain M04AcTs (GCA_029167205.1) as nomenclatural types of Methanocrinis natronophilus sp. nov. and Methanocrinis alkalitolerans sp. nov., respectively, which represent other species of the novel genus. This work demonstrates that the low energy aceticlastic methanogenesis may function at extreme conditions present in (halo)alkaline habitats. [ABSTRACT FROM AUTHOR]

Chemosynthetic ecosystems powered by microbial primary production are rare 'hot spots' of biological activity in the deep‐sea characterized by dense aggregations of specially adapted animal species. Among settings where such systems have been found, serpentinite‐hosted seep systems supported by alkaline geofluid are particularly understudied with just a few known sites worldwide. Mariana Forearc hosts the world's only series of active serpentinite mud volcanoes, but seep communities have only been reported from South Chamorro Seamount where large bathymodioline mussels dominate. Here, we report the discovery of a serpentinite‐hosted seep on the conical summit of Asùt Tesoru Seamount, Mariana Forearc. Named the 'Big Blue Seep', this field features white, likely carbonate crusts inhabited by animals, under which fluid seepage could be seen. We confirm 16 animal species, including typical seep‐associated fauna such as Desbruyeresia gastropods and Acharax awning‐clams. This is surprising as previous research expeditions did not notice any sign of chemosynthesis‐based ecosystems on this seamount, although the community is indeed difficult to spot due to the lack of large‐bodied epifauna such as mussels. The Big Blue Seep is adjacent to three drill holes made by the International Ocean Discovery Program expedition 366 (Holes U1496A‐C), which may have impact on seepage. Our findings represent the second chemosynthesis‐based ecosystem associated with serpentinite mud volcanism, suggestive of further such communities on other Mariana Forearc mud volcanoes. [ABSTRACT FROM AUTHOR]

The South Caspian Basin, the northern Alborz Mountains, the Gorgan plain and the Moghan plain constitute the northernmost and youngest petroleum system in Iran. This region was part of the Paratethys realm from Oligocene to Pliocene time. The Oligocene – Miocene Maikop/Diatom Total Petroleum System of the South Caspian Basin produces major volumes of hydrocarbons in Azerbaijan and Turkmenistan, and the Iranian sector of the basin has consequently undergone exploration due to its generally similar geology. The 20 km thick, dominantly Cenozoic sedimentary cover in the basin is reduced to less than 3 km in the northern foothills of the Alborz Mountains, and scattered surface oil seepages in the latter region are believed to be generated by Cretaceous and Miocene source rocks. In the Moghan plain to the southwest of the South Caspian Basin, anticlinal folds of Oligo‐Miocene Zivar Formation sandstones may be prospective for hydrocarbon exploration. Mud volcanoes in the Gorgan plain and in adjacent offshore regions at the SE margin of the South Caspian Basin are associated with hydrocarbon seepages, and appear to be sourced by Cretaceous and Cenozoic shales and mudstones. Major structural features in the southern part of the South Caspian Basin include Cenozoic mud diapirs, folds and gravity structures. [ABSTRACT FROM AUTHOR]

Identification of methane origins remains a challenging work as current diagnostic signals are often not sufficient to resolve individual formation and post‐formation processes. To address such a knowledge gap in a tectonically active and fragmented terrain, samples from mud volcanoes, gas seeps, and springs distributed along structural features onshore and offshore of Taiwan were analyzed for their isotopic compositions of methane, nitrogen, helium, dissolved inorganic carbon, CO2, and water. Our analyses yielded Δ13CH3D and Δ12CH2D2 values ranging between +1.9‰ and +7.8‰ and between +3.0‰ and +19.9‰, respectively. A portion of the samples were characterized by values that represent the thermodynamic equilibrium at temperatures of 99°–260°C. These temperature estimates, together with the bulk isotopic compositions and local geothermal gradients (25°–30°C/km), suggest that methane was formed by thermal maturation of organic matter at depths of 2–9 km below the land surface and channeled upward along faults. Other samples were found to deviate from equilibrium by varying degrees. Considering the geological background, helium isotopic ratios, and nitrogen isotopologue compositions, and methanogens detected at some sites, these gases are either abiotic in origin or a mixture of microbial and thermogenic sources. Regardless of whether the equilibrium of methane isotopologues was reached, few sites hosted by sedimentary formations were characterized by mantle‐like helium signatures, indicating decoupled origins and potential degassing of helium from the relic igneous source. Overall, these results suggest the extraction of methane and other gases from multiple depths from strata fragmented by fault displacement in an active orogenic belt. Plain Language Summary: Mud volcanoes and gas seeps are distributed primarily in active tectonic regimes and represent the surface expression of subsurface fracture networks. They provide rapid access to probing subsurface characteristics for the generations of methane, other gases, and water. Identifying the exact mechanisms of methane formation remains a challenging work due to the lack of diagnostic signals with sufficient resolving power. This study employed a wide range of isotopic tools to constrain the origins of gases and water from mud volcanoes and seeps in Taiwan, where dual subductions and associated arc‐continent collision between the Philippine Sea and Eurasian plates have enabled the plumbing of gases and water in accordance with structure development and stratum deformation. Our results reveal a spectrum of geochemical characteristics that point to diverse formation mechanisms and conditions. In particular, deeply sourced thermogenic methane (from depths of 2–9 km) appears to constitute a major gas component at most sites, and is mixed by various degrees with abiotic methane pertinent to igneous bodies emplaced during subduction/collision, or microbial methane generated at shallow depths. Overall, the results address the temporal and spatial variations in gas origins prone to terrain fragmentation and dynamic structural control associated with mountain building. Key Points: Mud volcanoes and gas seeps provide rapid access to probing subsurface fluid characteristics in tectonically active regionsThermogenic methane constitutes a major component of hydrocarbons and forms at temperatures of 99°–260°CA wide spectrum of geochemical characteristics indicates diverse formation mechanisms and conditions that constrain gas and water origins [ABSTRACT FROM AUTHOR]

In shallow subduction zones, fluid behavior impacts various geodynamic processes capable of regulating slip behaviors and forming mud volcanoes. However, evidence of structures that control the fluid transfer within an overriding plate is limited and the physical properties at the source faults of slow earthquakes are poorly understood. Here we present high-resolution seismic velocity models and reflection images of the Hyuga-nada area, Japan, where the Kyushu-Palau ridge subducts. We image distinct kilometer-wide columns in the upper plate with reduced velocities that extend vertically from the seafloor down to 10–13 km depth. We interpret the low-velocity columns as damaged zones caused by seamount subduction and suggest that they serve as conduits, facilitating vertical fluid migration from the plate boundary. The lateral variation in upper-plate velocity and seismic reflectivity along the plate boundary correlates with the distribution of slow earthquakes, indicating that the upper-plate drainage system controls the complex pattern of seismic slip at subduction faults. Vertical fluid pathways in the upper plate of the Hyuga-nada subduction zone, Japan, facilitate upward fluid migration from the plate boundary that host slow earthquakes and produce seafloor mud volcanoes. [ABSTRACT FROM AUTHOR]

A wide range of geological and geophysical methods was carried out on the Yamal Peninsula in the Arctic in the period 2014–2022. The results were analyzed together with data from remote sensing of the Earth. Fundamentally new data on the gas-dynamic mechanisms of dangerous processes in permafrost have been obtained. These data included catastrophic gas blowouts and explosions with the formation of giant craters. More than three thousand zones of powerful gas blowouts with the formation of craters at the bottom of thermokarst lakes, rivers, and the coast of the Kara Sea have been discovered. According to data on remote sensing of the Earth, large mud volcanic structures, located at the bottom of the Labvarto and Yambuto thermokarst lakes, were discovered on the Yamal Peninsula in 2022–2023 for the first time. Monitoring of their state with the use of retrospective satellite images showed the presence of periodic release of underground fluids, including gas. A conclusion was made about the discovery of active mud volcanoes on the Yamal Peninsula. [ABSTRACT FROM AUTHOR]

Pitted cones are cone-shaped structures, spanning from meters to kilometers in size, characterized by summit depressions. They are widely distributed on the surface of Mars with various origins, such as rootless cones, mud volcanoes, cinder or scoria cones, tuff rings or cones, pingos, and dirt cones. If the pitted cones identified in southern Utopia Planitia are mud volcanoes, as is speculated, they could be of particular interest due to the fact that mud volcanoes on Earth bring sediments from a depth of meters to kilometers to the surface. In this study, we have investigated the pitted cones near Zhurong rover's landing site in southern Utopia Planitia, utilizing recent images and digital elevation models obtained from the High Resolution Imaging Camera instrument onboard China's Tianwen-1 orbiter. By leveraging the high-resolution images and digital elevation models, we have conducted a geometric measurement to distinguish the origin of pitted cones in the vicinity of the Zhurong rover. The morphological characteristics of these pitted cones indicate an explosive mud volcano origin. These explosive mud volcanoes could have formed by the violent eruption of subsurface overpressurized sediments generated from the combined effect of overburden pressure and anomalous high heat flow. The sediments forming the pitted cones in the northern plains could be the remnants of an ancient ocean. With future in-situ observations of these pitted cones, we hope to gain further insights into the sediments of the putative northern ocean, as well as the physical and chemical properties of the Martian subsurface during the formation of the pitted cones. [ABSTRACT FROM AUTHOR]

The construction of a dam for the Irkutsk hydroelectric power plant caused the water level in Lake Baikal to increase by 80 cm between 1958 and 1961. This led to a downward migration of the base of the gas hydrate stability zone (BGHSZ) in the sediments of the lake, which was followed by a long transition process to a new state of equilibrium. In the first stage of the transition, new gas hydrates formed at the BGHSZ, which was accompanied and followed by a decrease in pore pressure, a decrease in methane transfer from the BGHSZ to the lake floor (via fast transfer pathways, such as faults or mud volcanoes), a decrease in the intensity of methane release from the lake floor into the water column, and a decrease in the methane concentrations in the water. In the second stage, which covers the last 10–15 years, methane concentrations in the water column have started to increase again, possibly in response to an uptick in methane flux from the lake floor. In this paper, we look at possible explanations. Mathematical modeling of the migration of the BGHSZ allowed us to estimate how long the transition process takes. The modeled transition times are different for different locations in the lake, depending mainly on the sedimentation rate and the gas hydrate content of the sediments. In the near future, Lake Baikal may reach a quasi-stationary state again similar to that before the construction of the dam. This stationary state likely involves much higher methane concentrations in the water column than what is observed today, as well as adverse effects on biota of pulsed expulsions of methane, sourced from the BGHSZ, into the water column by means of e.g. mud-volcano eruptions. Such effects may include events of mass deaths of the endemic deep-water fish, golomyanka, similar to what was reported to have occurred in the 19th and first half of the twentieth century, prior to the construction of the dam. This study also reemphasizes how variations in the dynamics of a natural gas hydrate system may have a profound impact on the water bodies in which they occur and on the ecosystems within these water bodies. It also highlights which effects can be expected in other hydrate-bearing marine basins where climate-induced sea-level rise will impact the dynamics of the hydrate reservoirs. [ABSTRACT FROM AUTHOR]

Active serpentinite mud volcanoes in the forearc region of the Izu‐Bonin‐Mariana system represent an excellent natural laboratory for studying the geochemical processes along convergent plate margins and the associated forearc. During IODP Expedition 366, serpentinite mud with lithic clasts from the underlying forearc crust and mantle as well as from the subducting Pacific Plate was recovered. Ultramafic clasts from Fantangisña Seamount reveal very high degrees of serpentinization with mesh and bastite textures as well as development of late lizardite and chrysotile veins, which suggests serpentinization temperatures below 200°C. On the other hand, recovered harzburgites and, on occasion, dunites from Asùt Tesoru Seamount show a well‐preserved primary assemblage with low degrees of serpentinization and forearc peridotite characteristics. Fine‐grained antigorite associating with lizardite has been identified throughout the serpentine mud matrix, suggesting an alteration temperature of c. 340°C. Furthermore, alteration conditions during rodingitization point to temperatures of at least 228°C, estimated via chlorite geothermometry. Additionally, a rare ophicarbonate clast containing andraditic as well as Cr‐rich hydrogarnets from Asút Tesoru Seamount indicates crystallization temperatures of at least 230°C. Hence, a trend of lower temperature of serpentinization and higher degree of alteration closer to the trench. The detailed characterization of the fluid‐rock alteration conditions as well as fluids composition and transport permits a better constraining of the fluid–rock interactions and related mass transfers within subduction zones and during ascent of serpentinite fault gouge within mud volcano conduits and in mudflows after their emplacement on the flanks of the edifices. Plain Language Summary: The fluid migration and circulation in subduction zones play a crucial role in the geochemical cycling as well as the physical and mechanical processes taking place there. Characterizing their nature, source and pathways would contribute to a better understanding not only of the rheology and fluid recycling but also of the tectonic and metamorphic processes operating deep within the Earth's lithosphere as a whole. During an International Ocean Discovery Program (IODP) Expedition, 366 serpentinite mud volcanoes located on the fractured forearc of the Mariana subduction system were drilled. The recovered material consists of highly hydrated rocks that experienced varying degrees of metamorphism and alteration. Mineralogical and chemical composition study of these rocks showed that they are former mantle rocks formed by the infiltration of fluids within the subduction zone. Some of them experienced additional transformation during their ascent to the seafloor by acquiring substantial amount of CO2‐rich minerals. Furthermore, the results show a trend in which alteration temperature is decreasing but transformation degree is increasing with proximity to the subduction channel. Key Points: Serpentinization and rodingitization in the subduction channel as well as carbonation in mud volcano conduits were identifiedOverall evolution of the slab‐derived fluid was narrowed down to temperatures from c. 350° to c. 100°C and belowSerpentinization degree increases with proximity to the trench [ABSTRACT FROM AUTHOR]